Telecommunication devices and methods

ABSTRACT

A terminal device includes receiver circuitry that receives parameter data from a base station in a cellular wireless telecommunication network. The terminal device also includes a storage device that stores an identifier that uniquely identifies the terminal device, and control circuitry that controls the terminal device. The control circuitry controls the terminal device, when operating in an idle mode, to perform cell reselection using at least one cell reselection parameter derived from the received parameter data and the stored unique identifier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/664,748, filed Jul. 31, 2017, which claims priority toPCT/EP2016/069025, filed Aug. 10, 2016, which claims priority toEuropean Patent Application No. 15186123.4, filed Sep. 21, 2015. Each ofthese applications are incorporated herein in their entirety byreference.

TECHNICAL FIELD

The present disclosure relates to telecommunication devices and methodsfor communicating data in a telecommunication system.

BACKGROUND

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Deploying multiple carriers is one of the most common solutions toaddress the ever increasing capacity needed in cellular networks,especially at traffic hotspots. This is noted in Work Item for Rel. 13,multicarrier load distribution in 3GPP TSG RAN Meeting #67 (RP-150611).This requires a balanced load among the multiple LTE carriers forefficient operation and optimal resources utilization. Load balancingacross multiple carriers should consider a variety of deploymentscenarios arising due to different capacities and the different numbersof the carriers available in a given area, especially whennon-contiguous spectrum with multi-carriers of different bandwidths ofdifferent bands is involved, resulting in different number of carrierswith different capacities in different areas.

For idle mode, it is observed that there is a strong correlation betweenthe idle mode terminal device density and the active terminal devicetraffic load in a cell within an LTE or other cellular network cell.Hence, control of the idle mode terminal device distribution is anessential element for traffic load balancing. However, it is difficultto conduct idle-mode load balancing by the current specified mechanismssuch as adjusting the reselection measurement threshold, broadcast ordedicated priorities. Furthermore, the deficiency in the current idlemode load balancing mechanisms has led to the partial reliance onredirection or handover (HO) after call establishment for loadbalancing. This has led to many more active redirections/HOs, increasingsignalling load and HO failure rates. Additionally, even if load balanceis achieved by HO and redirection, the situation will only last for ashort period of time since terminal device will eventually follow idlemode cell reselection rules. The situation is worse in HeterogeneousNetwork scenarios where the load in the different small cells at samefrequency layers might be different leading to ping-pongs and unevenidle terminal device distribution.

On the other hand, for connected mode, an ideal load balanced networkshould try to minimize active traffic overload probability whilemaximizing user throughput. However, current Reference Signal ReceiveQuality (RSRQ) based measurements as the HO and reselection metric maynot be a good representation of the achievable throughput. Othermeasurements such as Signal to Information Noise Ratio (SINR) may bemore appropriate for load-balancing active traffic so as to achieveoptimal throughput for the user, while simultaneously avoidingunnecessary HO or redirections.

Therefore, load balancing should preferably be achieved already at RRCconnection setup to minimize the need for load-triggered HO orredirection during connected mode. It is an aim of the presentdisclosure to address this issue

SUMMARY

According to the disclosure, there is provided a terminal devicecomprising receiver circuitry configured to receive parameter data froma base station in a cellular wireless telecommunication network, astorage device configured to store an identifier that uniquelyidentifies the terminal device and control circuitry configured tocontrol the terminal device, when operating in an idle mode, to performcell reselection using at least one cell reselection parameter derivedfrom the received parameter data and the stored unique identifier.

Various further aspects and features of the present disclosure aredefined in the appended claims and include a telecommunications device,a method of communicating data and circuitry for a telecommunicationdevice.

BRIEF DESCRIPTION OF DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 is a schematic diagram illustrating an example of a mobiletelecommunication system according to the present advancements;

FIG. 2 is a schematic diagram illustrating a LTE radio frame accordingto exemplary aspects of the present advancements;

FIG. 3 is a schematic diagram illustrating an example of a LTE downlinkradio subframe according to the present advancements;

FIG. 4 is a schematic of an example wireless telecommunications systemaccording to exemplary aspects of the present advancements; and

FIG. 5 is a flowchart of the process performed by the terminal deviceaccording to exemplary aspects of the present advancements.

DETAILED DESCRIPTION

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating in accordance with LTE principles and which may be adapted toimplement embodiments of the disclosure as described further below. Thenetwork 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from terminal devices104. Data is transmitted from base stations 101 to terminal devices 104within their respective coverage areas 103 via a radio downlink. Data istransmitted from terminal devices 104 to the base stations 101 via aradio uplink. The uplink and downlink communications are made usingradio resources that are licenced for use by the operator of the network100. The core network 102 routes data to and from the terminal devices104 via the respective base stations 101 and provides functions such asauthentication, mobility management, charging and so on. Terminaldevices may also be referred to as mobile stations, user equipment (UE),user terminal, terminal, mobile radio, and so forth. Base stations mayalso be referred to as transceiver stations/nodeBs/e-nodeBs, and soforth.

Mobile telecommunications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division modulation (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiple access scheme (SC-FDMA) on the radio uplink. FIG. 2 shows aschematic diagram illustrating an OFDM based LTE downlink radio frame201. The LTE downlink radio frame is transmitted from a LTE base station(known as an enhanced Node B) and lasts 10 ms. The downlink radio framecomprises ten subframes, each subframe lasting 1 ms. A primarysynchronisation signal (PSS) and a secondary synchronisation signal(SSS) are transmitted in the first and sixth subframes of the LTE frame.A physical broadcast channel (PBCH) is transmitted in the first subframeof the LTE frame.

FIG. 3 is a schematic diagram of a grid which illustrates the structureof an example conventional downlink LTE subframe. The subframe comprisesa predetermined number of symbols which are transmitted over a 1 msperiod. Each symbol comprises a predetermined number of orthogonalsubcarriers distributed across the bandwidth of the downlink radiocarrier.

The example subframe shown in FIG. 3 comprises 14 symbols and 1200subcarriers spread across a 20 MHz bandwidth licenced for use by theoperator of the network 100, and this example is the first subframe in aframe (hence it contains PBCH). The smallest allocation of physicalresource for transmission in LTE is a resource block comprising twelvesubcarriers transmitted over one subframe. For clarity, in FIG. 3 , eachindividual resource element is not shown, instead each individual box inthe subframe grid corresponds to twelve subcarriers transmitted on onesymbol.

FIG. 3 shows in hatching resource allocations for four LTE terminals340, 341, 342, 343. For example, the resource allocation 342 for a firstLTE terminal (UE 1) extends over five blocks of twelve subcarriers (i.e.60 subcarriers), the resource allocation 343 for a second LTE terminal(UE2) extends over six blocks of twelve subcarriers (i.e. 72subcarriers), and so on.

Control channel data can be transmitted in a control region 300(indicated by dotted-shading in FIG. 3 ) of the subframe comprising thefirst “n” symbols of the subframe where “n” can vary between one andthree symbols for channel bandwidths of 3 MHz or greater and where “n”can vary between two and four symbols for a channel bandwidth of 1.4MHz. For the sake of providing a concrete example, the followingdescription relates to host carriers with a channel bandwidth of 3 MHzor greater so the maximum value of “n” will be 3 (as in the example ofFIG. 3 ). The data transmitted in the control region 300 includes datatransmitted on the physical downlink control channel (PDCCH), thephysical control format indicator channel (PCFICH) and the physical HARQindicator channel (PHICH). These channels transmit physical layercontrol information. Control channel data can also or alternatively betransmitted in a second region of the subframe comprising a number ofsubcarriers for a time substantially equivalent to the duration of thesubframe, or substantially equivalent to the duration of the subframeremaining after the “n” symbols. The control data transmitted in thissecond region is transmitted on the enhanced physical downlink controlchannel (EPDCCH). This channel transmits physical layer controlinformation which may be in addition to that transmitted on otherphysical layer control channels.

PDCCH and EPDCCH contain control data indicating which subcarriers ofthe subframe have been allocated to specific terminals (or all terminalsor subset of terminals). This may be referred to as physical-layercontrol signalling/data. Thus, the PDCCH and/or EPDCCH data transmittedin the control region 300 of the subframe shown in FIG. 3 would indicatethat UE1 has been allocated the block of resources identified byreference numeral 342, that UE2 has been allocated the block ofresources identified by reference numeral 343, and so on.

PCFICH contains control data indicating the size of the control region(i.e. between one and three symbols for channel bandwidths of 3 MHz orgreater and between two and four symbols for channel bandwidths of 1.4MHz).

PHICH contains HARQ (Hybrid Automatic Request) data indicating whetheror not previously transmitted uplink data has been successfully receivedby the network.

Symbols in a central band 310 of the time-frequency resource grid areused for the transmission of information including the primarysynchronisation signal (PSS), the secondary synchronisation signal (SSS)and the physical broadcast channel (PBCH). This central band 310 istypically 72 subcarriers wide (corresponding to a transmission bandwidthof 1.08 MHz). The PSS and SSS are synchronisation signals that oncedetected allow a LTE terminal device to achieve frame synchronisationand determine the physical layer cell identity of the enhanced Node Btransmitting the downlink signal. The PBCH carries information about thecell, comprising a master information block (MIB) that includesparameters that LTE terminals use to properly access the cell. Datatransmitted to terminals on the physical downlink shared channel(PDSCH), which may also be referred to as a downlink data channel, canbe transmitted in other resource elements of the subframe. In generalPDSCH conveys a combination of user-plane data and non-physical layercontrol-plane data (such as Radio Resource Control (RRC) and Non AccessStratum (NAS) signalling). The user-plane data and non-physical layercontrol-plane data conveyed on PDSCH may be referred to as higher layerdata (i.e. data associated with a layer higher than the physical layer).

FIG. 3 also shows a region of PDSCH containing system information andextending over a bandwidth of R344. A conventional LTE subframe willalso include reference signals which are not shown in FIG. 3 in theinterests of clarity.

The number of subcarriers in a LTE channel can vary depending on theconfiguration of the transmission network. Typically this variation isfrom 72 sub carriers contained within a 1.4 MHz channel bandwidth to1200 subcarriers contained within a 20 MHz channel bandwidth (asschematically shown in FIG. 3 ). As is known in the art, datatransmitted on the PDCCH, PCFICH and PHICH is typically distributed onthe subcarriers across the entire bandwidth of the subframe to providefor frequency diversity.

The communications between the base stations 101 and the terminaldevices 104 are conventionally made using radio resources that have beenlicensed for exclusive use by the operator of the network 100. Theselicensed radio resources will be only a portion of the overall radiospectrum. Other devices within the environment of the network 100 may bewirelessly communicating using other radio resources. For example, adifferent operators network may be operating within the samegeographical region using different radio resources that have beenlicensed for use by the different operator. Other devices may beoperating using other radio resources in an unlicensed radio spectrumband, for example using Wi-Fi or Bluetooth technologies.

FIG. 4 schematically shows a telecommunications system 400 according toan embodiment of the disclosure. The telecommunications system 400 inthis example is based broadly on a LTE-type architecture. As such manyaspects of the operation of the telecommunications system 400 arestandard and well understood and not described here in detail in theinterest of brevity. Operational aspects of the telecommunicationssystem 400 which are not specifically described herein may beimplemented in accordance with any known techniques, for exampleaccording to the established LTE-standards and known variations thereof.

The telecommunications system 400 comprises a core network part (evolvedpacket core) 402 coupled to a radio network part. The radio network partcomprises a base station (evolved-nodeB) 404, a first terminal device406 and a second terminal device 408. It will of course be appreciatedthat in practice the radio network part may comprise a plurality of basestations serving a larger number of terminal devices across variouscommunication cells. However, only a single base station and twoterminal devices are shown in FIG. 4 in the interests of simplicity.

Although not part of the telecommunications system 400 itself, alsoshown in FIG. 4 are some other devices which are operable to wirelesslycommunicate with one another and which are operating within the radioenvironment of the telecommunications system 400. In particular, thereis a pair of wireless access devices 416 communicating with one anothervia radio link 418 operating in accordance with a Wi-Fi standard and apair of Bluetooth devices 420 communicating with one another via radiolink 422 operating in accordance with a Bluetooth standard. These otherdevices represent a potential source of radio interference for thetelecommunications system 400. It will be appreciated that in practicethere will typically be many more such devices operating in the radioenvironment of the wireless telecommunications system 400, and only twopairs of devices 416, 418 are shown in FIG. 4 for simplicity.

As with a conventional mobile radio network, the terminal devices 406,408 are arranged to wirelessly communicate data to and from the basestation (transceiver station) 404. The base station is in turncommunicatively connected to a serving gateway, S-GW, (not shown) in thecore network part which is arranged to perform routing and management ofmobile communications services to the terminal devices in thetelecommunications system 400 via the base station 404. In order tomaintain mobility management and connectivity, the core network part 402also includes a mobility management entity (not shown) which manages theenhanced packet service, EPS, connections with the terminal devices 406,408 operating in the communications system based on subscriberinformation stored in a home subscriber server, HSS. Other networkcomponents in the core network (also not shown for simplicity) include apolicy charging and resource function, PCRF, and a packet data networkgateway, PDN-GW, which provides a connection from the core network part402 to an external packet data network, for example the Internet. Asnoted above, the operation of the various elements of the communicationssystem 400 shown in FIG. 4 may be broadly conventional apart from wheremodified to provide functionality in accordance with embodiments of thedisclosure as discussed herein.

The terminal devices 406, 408 each comprise a transceiver unit 406 a,408 a for transmission and reception of wireless signals and acontroller unit 406 b, 408 b configured to control the operation of therespective devices 406, 408 in accordance with embodiments of thedisclosure. Within the transceiver units 406 a, 408 a transmittercircuitry and/or receiver circuitry may be provided. The respectivecontroller units 406 b, 408 b may each comprise a processor unit whichis suitably configured/programmed to provide the desired functionalitydescribed herein using conventional programming/configuration techniquesfor equipment in wireless telecommunications systems. For each of theterminal devices 406, 408, their respective transceiver units 406 a, 408a and controller units 406 b, 408 b are schematically shown in FIG. 4 asseparate elements for ease of representation. However, it will beappreciated that for each terminal device the functionality of theseunits can be provided in various different ways, for example using asingle suitably programmed general purpose computer, or suitablyconfigured application-specific integrated circuit(s)/circuitry, orusing a plurality of discrete circuitry/processing elements forproviding different elements of the desired functionality. It will beappreciated the terminal devices 406, 408 will in general comprisevarious other elements associated with their operating functionality inaccordance with established wireless telecommunications techniques (e.g.a power source, possibly a user interface, and so forth).

Moreover, within each terminal device 406, 408 is provided a storagedevice. The storage device stores a unique identifier. The uniqueidentifier is unique to each terminal device and is provided to uniquelyidentify and thus distinguish each terminal device from one another. Theunique identifier is, in embodiments of the disclosure, a UE Identifier(hereinafter “UE-ID”). Of course, any kind of unique identifier isenvisaged. For example, the unique identifier may be used to simplydefine into which group of terminal devices any one terminal device maybe provided. In other words, the unique identifier is not necessarily aglobally unique identifier, but may be any kind of identifier thatallows grouping of the terminal devices.

As has become commonplace in the field of wireless telecommunications,terminal devices may support Wi-Fi and Bluetooth functionality inaddition to cellular/mobile telecommunications functionality. Thus thetransceiver units 406 a, 408 a of the respective terminal devices maycomprise functional modules operable according to different wirelesscommunications operating standards. For example, the terminal devices'transceiver units may each comprise an LTE transceiver module forsupporting wireless communications in accordance with an LTE-basedoperating standard, a WLAN transceiver module for supporting wirelesscommunications in accordance with a WLAN operating standard (e.g. aWi-Fi standard), and a Bluetooth transceiver module for supportingwireless communications in accordance with a Bluetooth operatingstandard. The underlying functionality of the different transceivermodules may be provided in accordance with conventional techniques. Forexample, a terminal device may have separate hardware elements toprovide the functionality of each transceiver module, or alternatively,a terminal device might comprise at least some hardware elements whichare configurable to provide some or all functionality of multipletransceiver modules. Thus the transceiver units 406 a, 408 a of theterminal devices 406, 408 represented in FIG. 4 are assumed here toprovide the functionality of an LTE transceiver module, a Wi-Fitransceiver module and a Bluetooth transceiver module in accordance withconventional wireless communications techniques.

The base station 404 comprises a transceiver unit 404 a for transmissionand reception of wireless signals and a controller unit 404 b configuredto control the base station 404. The controller unit 404 b may comprisea processor unit which is suitably configured/programmed to provide thedesired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. The transceiver unit 404 a and thecontroller unit 404 b are schematically shown in FIG. 4 as separateelements for ease of representation. However, it will be appreciatedthat the functionality of these units can be provided in variousdifferent ways, for example using a single suitably programmed generalpurpose computer, or suitably configured application-specific integratedcircuit(s)/circuitry or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the base station 404 willin general comprise various other elements associated with its operatingfunctionality. For example, the base station 404 will in generalcomprise a scheduling entity responsible for scheduling communications.The functionality of the scheduling entity may, for example, be subsumedby the controller unit 404 b.

Thus, the base station 404 is configured to communicate data with thefirst and second terminal devices 406, 408 over respective first andsecond radio communication links 410, 412.

As will be appreciated by the skilled person, the terminal devices 406,408 operate in two modes. The first mode is the Radio Resource Control(RRC) idle mode (hereinafter “idle mode”) and the RRC connected mode(hereinafter “connected mode”). The idle mode is where radio is notactive, but an identity is provided to the terminal device and trackedby the network. The connected mode is where there is active radiooperation with the base station and the network.

In the idle mode, cell-reselection and associated measurements takeplace. Additionally, other steps such as i) network selection isperformed and ii) System Information Broadcast Blocks (SIB blocks) aremonitored. The present disclosure relates to cell-reselection in theidle mode.

Cell-Reselection

A terminal device performs cell-reselection when the serving cell'sradio carrier strength is poor or a suitable high strength neighbourcell is available. In order to allow the terminal device to know ontowhich frequencies or cells to measure, and to provide the parametersused for evaluating which frequency or cell to (re)select, the basestation provides each terminal device with a list of frequencies andcells and their associated cell reselection priorities, thresholds andoffsets to be used in cell reselection evaluation. This list of cellsmay be specified in any of SIB4, 5, 6, 7 and RRC Connection Release aswould be appreciated by the skilled person.

In other words, after an initial selection of a cell, and according to adefined set of criteria the terminal device measures the RSRP of theselected cell and the neighbouring cells and if the cell reselectioncriteria is met, cell-reselection will be performed. The cellreselection priorities and the associated thresholds and offsets arechosen by the network. This known mechanism of cell reselection has adrawback.

The current mechanism does not allow load balancing across multiplecarriers when terminal devices operate in idle mode.

Presently, two different mechanisms have been discussed to address thisload balancing issue. The first mechanism is a continuous randomisationmechanism and the second mechanism is a “one-shot” mechanism.

Continuous Randomisation Mechanism

In this mechanism the known cell reselection mechanism and rules will befollowed as much as possible. However, in addition, a randomisationelement will be applied at each terminal device. In general, a terminaldevice will generate one random number which will then be comparedagainst one or more pre-configured parameters in order to decide whetherreselection to one candidate cell will occur or not. The redistributionof terminal devices (or the load balancing) is realised by havingstatistically distributed random values. The pre-configured parameterswill therefore need to be periodically broadcast or provided in thesystem information.

This mechanism has a number of drawbacks. Firstly, as the randomisationscheme within each terminal device determines the load balancing, thenetwork has little control over the load balancing. This is particularlyundesirable as the behaviour of terminal devices in situations like thiscan be unpredictable. A second drawback is that some companies have hadlegal issues in the past with schemes involving drawing a random numberand so are apprehensive about adopting such a scheme. This will reducethe effectiveness of such a load balancing scheme if there is littleadoption.

“One-Shot” Mechanism

In this mechanism the network will redistribute the terminal devices ifthe network discovers an imminent congestions situation. A terminaldevice (or a group of terminal devices) can be paged for the purpose ofload balancing. The paging message may contain a trigger to activatepreviously (i.e. in RRC Connection Release) acquired DedicatedPriorities. When the trigger is received, the terminal device(s) startappropriate timer and apply the dedicated priorities. The paging messagemay also contain a de-prioritisation request to instruct the terminaldevice(s) that currently prioritized carrier/cell should be temporarilyassigned the lowest priority. This will be for a period of time set by atimer. Alternatively, the paging message may contain a prioritisationrequest to temporarily assign the highest priority to a certaincarrier/cell. Eventually, the paging message can comprise a whole newset of priorities. These priorities are similar to Dedicated Prioritiesand are aimed for a subset of terminal devices, if the network discoversthat previously sent priorities will not suffice to mitigate currentload situation. New parameters in the paging message are needed in orderto run abovementioned actions (e.g. new priority or intended reselectiontarget frequency/cell).

This mechanism has drawbacks too. Firstly, as is apparent from theabove, this mechanism is complex and requires a high paging load. Aseach individual terminal device needs to be individually paged anddedicated priorities provided, this creates an excessive load. Inaddition, most operators do not implement and do not wish to implementdedicated priorities, for instance cell reselection priorities providedin RRC connection release or otherwise by dedicated signalling.

It is an aim of the disclosure to address the load balancing issue inidle mode without the drawbacks of the two above noted mechanisms.

In a terminal device according to embodiments of the disclosure has aunique identifier. The unique identifier is described with reference toFIG. 4 . The unique identifier is stored within the terminal device anduniquely identifies the terminal device from other terminal devices.

It is envisaged that any previously provided UE-identifier (UE-ID) maybe used as the unique identifier, although the disclosure is not solimited. For example, the International Mobile Equipment Identity (IMEI)or the International Mobile Subscriber Identity (IMSI) or a radionetwork temporary identifier (RNTI) may be used as the uniqueidentifier.

The network broadcasts (or otherwise provides to the terminal device)parameters which will be used with the UE-ID to provide load balancing.The parameters may be broadcast to the terminal devices within a cell ormay be provided over dedicated signalling such as the RRC ConnectionRelease, or may be provided in advance to the terminal device. Theparameters will be explained later.

The parameters provided to the terminal devices include at least one ofthe following two parameters.

The first is multiple cell reselection offsets. The cell reselectionoffset that will be used by the terminal device will be selected basedon the UE-ID. The second parameter is the multiple absolute prioritiesfor the frequency or cell. The priority used by the terminal device,again, will be selected based on the UE-ID.

In addition to the above two parameters, the network will provide aparameter controlling the percentage of terminal devices applying aspecific offset or priority or a parameter controlling the amount ofoffset or relative priority applied (depending upon which of the aboveparameters are provided). In this case, it should be noted that thenetwork may provide either the parameter controlling the percentage orthe parameter controlling the amount of offset, or alternatively thenetwork may provide both of these parameters.

To illustrate the above, let us consider the example of a networkproviding multiple priority levels for a particular cell (priority A=1,priority B=2) and 40% of the terminal devices should use priority A and60% should use priority B.

In order to determine whether the terminal device should use priority Aor priority B, the terminal device checks its UE-ID and if, for example,the last digit in the UE-ID is a 0, 1, 2, 3 then then terminal deviceknows it must use priority A and if the last digit in the UE-ID is 4, 5,6, 7, 8, 9, then the terminal device knows it must use priority B. Asthe likelihood of any terminal device having a particular last digit inits UE-ID is statistically equal, then the load will be balanced. Thisallows the network, with certainty, to know that the load will bebalanced without the complex paging of the one shot mechanism. Ofcourse, although the final digit is noted above, any particular featureof the UE-ID may be used to determine the selection of the parameter. Adetailed example is provided later.

A more detailed description of the parameters is now provided.

Multiple Cell Reselection Offsets

Currently the network can broadcast a cell-specific and/or frequencyspecific offset which the terminal device applies to the cellreselection evaluation according to the rules set out in 3GPP TS 36.304.The network also broadcasts a hysteresis value to be applied.

Qoffset_(s,n)

This specifies the offset between the two cells.

Qoffset_(frequency)

Frequency specific offset for equal priority E-UTRAN frequencies.

Q_(hyst)

This specifies the hysteresis value for ranking criteria.

For intra-frequency and equal priority frequencies, the terminal deviceperforms ranking according to the following criteria using theparameters mentioned above, along with the RSRP measurements of thecurrent and neighbouring cells.

The cell-ranking criterion R_(s) for serving cell and Rn forneighbouring cells is defined by:R _(s) =Q _(meas,s) +Q _(Hyst) −Qoffset_(temp)R _(n) =Q _(meas,n) −Qoffset−Qoffset_(temp)where:

Q_(meas) RSRP measurement quantity used in cell reselections. QoffsetFor intra-frequency: Equals to Qoffset_(s,n), if Qoffset_(s,n) is valid,otherwise this equals to zero. For inter-frequency: Equals toQoffset_(s,n) plus Qoffset_(frequency), if Qoffset_(s,n) is valid,otherwise this equals to Qoffset_(frequency). Qoffset_(temp) Offsettemporarily applied to a cell

In one embodiment of this disclosure, the network broadcasts two or morevalues for either offset or hysteresis, and the terminal device appliesone of those values depending on a function of UE-ID.

Multiple Absolute Priorities

Currently the network signals an absolute priority to be applied to aspecific frequency when performing cell reselection evaluation. Inaddition, it may be possible for the network to provide cell-specificabsolute priority in order to distribute terminal devices amongst cellson the same frequency. For example, small cells may be used for capacityincrease. In addition, cell reselection thresholds are, in embodiments,provided for each of the frequencies and/or cells.

CellReselectionPriority

This specifies the absolute priority for E-UTRAN frequency or UTRANfrequency or group of GERAN frequencies or band class of CDMA2000 HRPDor band class of CDMA2000 1×RTT.

Thresh_(X, HighP)

This specifies the Srxlev threshold (in dB) used by the terminal devicewhen reselecting towards a higher priority RAT/frequency than thecurrent serving frequency. Each frequency of E-UTRAN and UTRAN, eachgroup of GERAN frequencies, each band class of CDMA2000 HRPD andCDMA2000 1×RTT might have a specific threshold.

Thresh_(X, HighQ)

This specifies the Squal threshold (in dB) used by the terminal devicewhen reselecting towards a higher priority RAT/frequency than thecurrent serving frequency. Each frequency of E-UTRAN and UTRAN FDD mighthave a specific threshold.

Thresh_(X, LowP)

This specifies the Srxlev threshold (in dB) used by the terminal devicewhen reselecting towards a lower priority RAT/frequency than the currentserving frequency. Each frequency of E-UTRAN and UTRAN, each group ofGERAN frequencies, each band class of CDMA2000 HRPD and CDMA2000 1×RTTmight have a specific threshold.

Thresh_(X, LowQ)

This specifies the Squal threshold (in dB) used by the terminal devicewhen reselecting towards a lower priority RAT/frequency than the currentserving frequency. Each frequency of E-UTRAN and UTRAN FDD might have aspecific threshold.

Thresh_(Serving, LowP)

This specifies the Srxlev threshold (in dB) used by the terminal deviceon the serving cell when reselecting towards a lower priorityRAT/frequency.

Thresh_(Serving, LowQ)

This specifies the Squal threshold (in dB) used by the terminal deviceon the serving cell when reselecting towards a lower priorityRAT/frequency.

As noted above, the reselection rules are defined in 3GPP TS 36.304section 5.2.4.5 for different priority layers (where layer meansfrequency or RAT). However, in the context of the present disclosure,the most important two rules are

1) Higher Priority

A cell of a higher priority UTRAN TDD, GERAN or CDMA2000 RAT/frequencyfulfils Srxlev>Thresh_(X, HighP) during a time intervalTreselection_(RAT).

2) Lower Priority

Cell reselection to a cell on a lower priority E-UTRAN frequency orinter-RAT frequency than the serving frequency shall be performed if:

-   -   The serving cell fulfils Srxlev<Thresh_(Serving, LowP) and a        cell of a lower priority RAT/frequency fulfils        Srxlev>Thresh_(X, LowP) during a time interval        Treselection_(RAT);

In one embodiment of this disclosure, the network broadcasts two or morevalues for this cellReselectionPriority. Optionally to the embodiment,multiple thresholds may also be broadcast, and the terminal deviceapplies one of those values depending on the UE-ID.

Parameter Controlling the Percentage of UEs Applying a Specific Offsetor Priority

In order to explain this parameter, we need to use some examples of whatthe function of UE-ID could be.

In one embodiment of the disclosure, the UE-ID may be the identifierused by the terminal device to calculate paging occasions and pagingframes. This is in accordance with 3GPP TS 36.304 (the relevant sectionbeing provided in Annex A).

The intention of the calculation for paging occasions shown in Annex A,is to distribute terminal devices evenly amongst the availableresources. In other words, for any specific terminal device the functionis not random, when you consider all of the terminal devices in thecell, this is randomised and evenly distributed.

One possibility for this disclosure is to always distribute terminaldevices evenly amongst the allowed/signalled offsets or priorities.However, this does not meet the requirement that the network should beable to control what percentage (or fraction) of terminal devices aredistributed to what frequency. Therefore, it would be beneficial tocontrol the percentage of terminal devices. It might also be beneficialto explicitly specify which UE-IDs shall apply which priority.

A more detailed example as briefly explained above is now provided.

In the following example the network broadcasts the percentage (e.g. aninteger value ranging from 0 (0%) to 10 (100%). Let's call the value N.

For example the network broadcasts the value N=4 (40%).

The terminal device calculates UE-ID mod 10—which will result in a valuefrom 0-9.

If the value is <4 then the terminal device selects the first priority.If the value is >=4 then the terminal device selects the secondpriority. This function can be written as

If UE-ID mod 10<N

Select First Priority

Else

Select Second Priority

This allows the network to control the percentage of terminal devicesselecting the first signalled priority (which might be relatively low)and the percentage of terminal devices selecting the second signalledpriority (which might be relatively high) and hence achieving theobjective of distributing a fraction of the terminal devices amongstfrequencies or cells. Either the first or second priority could be alegacy signalled value. As would be appreciated, the legacy signalledvalue is a value currently sent in System Information to all terminaldevices. This value, in embodiments, may also be sent with an additionalpriority as an alternative value depending on the UE-ID. The absence ofthe value N could indicate equal distribution (50/50 split amongst thetwo signalled priorities—so N=5). In other words, the terminal devicewill assume a distribution unless told by the network. In this case, thenetwork will inform the terminal device of the change. That is, thevalue N provided by the network might be added or subtracted to thelegacy signalled value (for example if N=2 and legacy value=3 thenadditional priority value=5). This default assumption has the advantagethat should the default be the usual choice of the network, thensignalling will be reduced as the network will only signal the terminaldevice(s) should the default assumption not be correct.

One additional option is to use a fixed offset or priority value (or adefault if not signalled)—for example if the second priority is notsignalled, then the terminal device applies the highest (or lowest)possible priority if the UE-ID function is satisfied

The same idea can be applied for a list of more than two priorities. Thenetwork would just then signal the percentage of terminal devices toapply each of the priorities.

An additional control parameter could apply an offset to UE-ID. Thiswould allow the network to vary which of the UE-IDs apply whichpriority. For example offset value would be a number in the range 0-9called “X”.

If (UE−ID+X) mod 10<N

Select first priority

Else

Select second priority

The network might periodically update the parameter X, to allowdifferent sets of terminal devices to communicate with the base stationon different frequencies.

Another alternative is to provide a list specifying precisely whichUE-ID applies which priority. For example, along with the firstsignalled priority the network provides a list of numbers in the range0-9. For example priority 1 is signalled along with values 1, 4, 5, 7.Then all terminal devices with UE-ID mod 10=1, 4, 5, or 7 shall applythis priority, and other UE-ID shall apply another priority (which mightbe the default legacy value).

Parameter Controlling the Amount of Offset, or Relative Priority

This parameter would be used as an alternative to signalling explicitpriorities or offsets and using the UE-ID to specify the percentage orfraction.

Instead of selecting one of the signalled values, the terminal devicecalculates a priority or offset based on the UE-ID.

For example, currently the cell reselection priority can be given avalue 0-7. Therefore to evenly spread the priorities a function could beused as follows.UE-ID mod 8=cell reselection priority.

Similarly, the applied offset could be calculated based on UE-IDUE-ID mod 4*signalledOffset=Offset

FIG. 5 shows a flowchart 500 showing the steps carried out by theterminal device. The process starts at step 505. The terminal devicereceives the parameter data from the base station in step 510. AlthoughFIG. 5 refers to receiving the parameter data during idle mode (forexample in system information broadcast and/or paging), as noted above,the disclosure is not so limited and the parameter data may be providedduring the RRC connection release or at any appropriate time. Theterminal device then uses its unique identifier (for example the UE-ID)and the parameter data to determine the cell-reselection in step 515.The terminal device then performs cell-reselection in step 520. Theprocess ends at step 525.

Discontinuous Reception for Paging

The following is a brief description of discontinuous reception forpaging according to exemplary aspects the advancements described herein.

The UE may use Discontinuous Reception (DRX) in idle mode in order toreduce power consumption. One Paging Occasion (PO) is a subframe wherethere may be P-RNTI transmitted on PDCCH addressing the paging message.One Paging Frame (PF) is one Radio Frame, which may contain one ormultiple Paging Occasion(s). When DRX is used the UE needs only tomonitor one PO per DRX cycle.

PF and PO is determined by following formulae using the DRX parametersprovided in System Information:

PF is given by following equation:SFN mod T=(T div N)*(UE_ID mod N)Index i_s pointing to PO from subframe pattern defined in 7.2 will bederived from following calculation:i_s=floor(UE_ID/N)mod Ns

System Information DRX parameters stored in the UE shall be updatedlocally in the UE whenever the DRX parameter values are changed in SI.If the UE has no IMSI, for instance when making an emergency callwithout USIM, the UE shall use as default identity UE_ID=0 in the PF andi_s formulas above.

The following Parameters are used for the calculation of the PF and i_s:

-   -   T: DRX cycle of the UE. T is determined by the shortest of the        UE specific DRX value, if allocated by upper layers, and a        default DRX value broadcast in system information. If UE        specific DRX is not configured by upper layers, the default        value is applied.    -   nB: 4T, 2T, T, T/2, T/4, T/8, T/16, T/32.    -   N: min(T,nB)    -   Ns: max(1,nB/T)    -   UE_ID: IMSI mod 1024.

IMSI is given as sequence of digits of type Integer (0 . . . 9), IMSIshall in the formulae above be interpreted as a decimal integer number,where the first digit given in the sequence represents the highest orderdigit.

For example:IMSI=12(digit1=1,digit2=2)

In the calculations, this shall be interpreted as the decimal integer“12”, not “1×16+2=18”.

The present disclosure, although discussed in respect of (andparticularly suitable to) a 3GPP- and optionally LTE-mobile system, isnot limited to these examples. Likewise, although the description usesterms which can sometimes be based on current names or features of the3GPP or other standards, the teachings of the present disclosure are notlimited to this existing procedures or standards and are intended toapply to any suitable arrangement.

The following clauses define further example aspects and features of thepresent technique:

1. A terminal device comprising receiver circuitry configured to receiveparameter data from a base station in a cellular wirelesstelecommunication network, a storage device configured to store anidentifier that uniquely identifies the terminal device and controlcircuitry configured to control the terminal device, when operating inan idle mode, to perform cell reselection using at least one cellreselection parameter derived from the received parameter data and thestored unique identifier.

2. A terminal device according to clause 1, wherein the identifier is aUE Identifier.

3. A terminal device according to clause 2, wherein the UE Identifier isan International Mobile Subscriber Identity.

4. A terminal device according to clause 1, 2 or 3 wherein the cellreselection parameter is one of a multiple cell reselection offsets ormultiple absolute priorities for the frequency or cell.

5. A terminal device according to clause 4, wherein the parameter datacontains multiple cell reselection offsets or multiple absolutepriorities for the frequency or cell.

6. A terminal device according to clause 4, wherein the controlcircuitry is configured to calculate a priority or offset based on theunique identifier.

7. A terminal device according to clause 4, wherein the parameter datafurther includes either i) a parameter controlling a percentage ofterminal devices applying a specific offset value or priority or ii) aparameter controlling the amount of offset or relative priority applied.

8. A terminal device according to clause 4, wherein the offset valueprovides a difference value from a default percentage.

9. A terminal device according to clause 6, wherein the offset valueprovides a difference value from a default percentage.

10. A terminal device according to clause 7, wherein the parameter datafurther includes an offset to be applied to the stored uniqueidentifier.

11. A communication system comprising a base station in in communicationwith a terminal device according to any one of clauses 1 to 10.

12. A method of operating a terminal device in a cellular wirelesstelecommunication network, the method comprising receiving parameterdata from a base station in the cellular wireless telecommunicationnetwork, storing an identifier that uniquely identifies the terminaldevice and controlling the terminal device, when operating in an idlemode, to perform cell reselection using at least one cell reselectionparameter derived from the received parameter data and the stored uniqueidentifier.

13. A method according to clause 12, wherein the identifier is a UEIdentifier.

14. A method according to clause 13, wherein the UE Identifier is anInternational Mobile Subscriber Identity.

15. A method according to clause 12, 13 or 14 wherein the cellreselection parameter is one of a multiple cell reselection offsets ormultiple absolute priorities for the frequency or cell.

16. A method according to clause 15, wherein the parameter data containsmultiple cell reselection offsets or multiple absolute priorities forthe frequency or cell.

17. A method according to clause 15, comprising calculating a priorityor offset based on the unique identifier.

18. A method according to clause 15, wherein the parameter data furtherincludes either i) a parameter controlling a percentage of terminaldevices applying a specific offset value or priority or ii) a parametercontrolling the amount of offset or relative priority applied.

19. A method according to clause 15, wherein the offset value provides adifference value from a default percentage.

20. A method according to clause 17, wherein the offset value provides adifference value from a default percentage.

21. A method according to clause 18, wherein the parameter data furtherincludes an offset to be applied to the stored unique identifier.

22. A computer program product comprising computer readable instructionswhich, when loaded onto a computer, configures the computer to perform amethod according to any one of clause 12 to 21.

The invention claimed is:
 1. A terminal device comprising: receivercircuitry configured to receive at least one system information blockincluding parameter data from a base station in a cellular wirelesstelecommunication network, the parameter data including at leastabsolute priorities for frequencies; a storage device configured tostore an identifier that uniquely identifies the terminal device; andcontrol circuitry configured to control the terminal device, whenoperating in an idle mode, to perform cell reselection based on theabsolute priorities for frequencies included in the received parameterdata and based on a result of a comparison operation performed with anumerical value of the stored unique identifier, wherein the controlcircuitry is configured to calculate an offset used during the cellreselection based on a value of only a last digit of the uniqueidentifier.
 2. The terminal device according to claim 1, wherein theresult of the comparison operation indicates a result of a mathematicalcomparison between a value calculated based on the numerical value ofthe stored unique identifier and a value based on a predeterminednumber.
 3. The terminal device according to claim 1, wherein theabsolute priorities for frequencies identify an absolute priority foreach of a plurality of possible frequencies, and wherein the controlcircuitry is further configured to determine a plurality of availablefrequencies at a plurality of target cells, identify one of theplurality of available frequencies having the highest absolute priorityin the absolute priorities for frequencies, and control the circuitry toperform the cell reselection by selecting one of the plurality of targetcells having the identified highest priority frequency.
 4. The terminaldevice according to claim 1, wherein the identifier includes anInternational Mobile Subscriber Identity (IMSI).
 5. The terminal deviceaccording to claim 1, wherein the parameter data further includes eitheri) a parameter controlling a percentage of terminal devices applying aspecific offset value or priority or ii) a parameter controlling theamount of offset or relative priority applied.
 6. A terminal devicecomprising: receiver circuitry configured to receive at least one systeminformation block including parameter data from a base station in acellular wireless telecommunication network, the parameter dataincluding at least absolute priorities for frequencies; a storage deviceconfigured to store an identifier that uniquely identifies the terminaldevice; and control circuitry configured to control the terminal device,when operating in an idle mode, to perform cell reselection based on theabsolute priorities for frequencies included in the received parameterdata and based on a result of a comparison operation performed with anumerical value of the stored unique identifier, wherein multiple cellreselection offsets included in the parameter data provide differencevalues from a default percentage.
 7. The terminal device according toclaim 1, wherein the parameter data further includes an offset to beapplied to the stored unique identifier.
 8. A communication systemcomprising: the terminal device according to claim 1; and a base stationin communication with the terminal device.
 9. A method of operating aterminal device in a cellular wireless telecommunication network, themethod comprising: receiving at least one system information blockincluding parameter data from a base station in the cellular wirelesstelecommunication network, the parameter data including at leastabsolute priorities for frequencies; storing an identifier that uniquelyidentifies the terminal device; controlling the terminal device, whenoperating in an idle mode, to perform cell reselection based on theabsolute priorities for frequencies included in the received parameterdata and based on a result of a comparison operation performed with anumerical value of the stored unique identifier; and calculating anoffset used during the cell reselection based on a value of only a lastdigit of the unique identifier.
 10. The method according to claim 9,wherein the result of the comparison operation indicates a result of amathematical comparison between a value calculated based on thenumerical value of the stored unique identifier and a value based on apredetermined number.
 11. The method according to claim 9, wherein theabsolute priorities for frequencies identify an absolute priority foreach of a plurality of possible frequencies, and wherein the methodfurther comprises determining a plurality of available frequencies at aplurality of target cells, identifying one of the plurality of availablefrequencies having the highest absolute priority in the absolutepriorities for frequencies, and controlling the circuitry to perform thecell reselection by selecting one of the plurality of target cellshaving the identified highest priority frequency.
 12. The methodaccording to claim 9, wherein the identifier includes an InternationalMobile Subscriber Identity (IMSI).
 13. The method according to claim 9,wherein the parameter data further includes either i) a parametercontrolling a percentage of terminal devices applying a specific offsetvalue or priority or ii) a parameter controlling the amount of offset orrelative priority applied.
 14. A method of operating a terminal devicein a cellular wireless telecommunication network, the method comprising:receiving at least one system information block including parameter datafrom a base station in the cellular wireless telecommunication network,the parameter data including at least absolute priorities forfrequencies; storing an identifier that uniquely identifies the terminaldevice; controlling the terminal device, when operating in an idle mode,to perform cell reselection based on the absolute priorities forfrequencies included in the received parameter data and based on aresult of a comparison operation performed with a numerical value of thestored unique identifier, wherein multiple cell reselection offsetsincluded in the parameter data provide difference values from a defaultpercentage.
 15. The method according to claim 9, wherein the parameterdata further includes an offset to be applied to the stored uniqueidentifier.
 16. A non-transitory computer-readable medium encoded withcomputer readable instructions that, when executed by a computer, causethe computer to perform the method according to claim
 9. 17. A basestation device comprising: transmitter circuitry configured to transmitat least one system information block including parameter data from to aterminal device in a cellular wireless telecommunication network, theparameter data including at least absolute priorities for frequencies;and control circuitry configured to control the base station to performcell reselection in the terminal device, when the terminal device isoperating in an idle mode, and when the terminal device performs thecell reselection based on the absolute priorities for frequenciesincluded in the transmitted parameter data and based on a result of acomparison operation performed with a numerical value of a uniqueidentifier stored in the terminal device, wherein the terminal device isconfigured to calculate an offset used during the cell reselection basedon a value of only a last digit of the unique identifier.